Measurement of Local Plastic Deformation in Aluminum Alloy by Means of X-ray 3D Imaging Technique

AbstractTo understand the local deformation behavior is very important for improvement of deformability in aluminum alloys which possess poor deformation limit in comparison with steels. However, measurement of local deformation in the interior of metal is not sufficiently carried out. In this study, the development of local plastic strain is measured by means of X-ray 3D imaging technique, i.e. high-resolution synchrotron X-ray microtomography. The marker tracking method, which is based on 3D image processing in volumetric image, is developed for obtaining local strains in 3D. Deformation behaviour is particularly different in individual grains. It was found that grains with different orientations deform maintaining harmony by shear deformation

Applicability of correlated digital image correlation and infrared thermography for measuring mesomechanical deformation in foams and auxetics

Cellular materials such as metal foams or auxetic metamaterials are interesting microheterogeneous materials used for lightweight construction and as energy absorbers. Their macroscopic behavior is related to their specific mesoscopic deformation by a strong structure-property-relationship. Digital image correlation and infrared thermography are two methods to visualize and study the local deformation behavior in materials. The present study deals with the full-field thermomechanical analysis of the mesomechanical deformation in Ni/PU hybrid foams and Ni/polymer hybrid auxetic structures performing a correlative digital image correlation and infrared thermography. Instead of comparing and correlating only the primary output variables of both methods, strain and temperature, also strain rates and temperature rates occurring during deformation were compared. These allow for a better correlation and more conclusive results than obtained using only the primary output variables

NASTRAN analysis of an air storage piping system

The application of NASTRAN to a complex piping design evaluation problem is summarized. Emphasis is placed on structural modeling aspects, problems encountered in modeling and analyzing curved pipe sections, principal results, and relative merits of using NASTRAN as a pipe analysis and design tool. In addition, the piping and manifolding system was analyzed with SNAP (Structural Network Analysis Program). The parallel SNAP study provides a basis for limited comparisons between NASTRAN and SNAP as to solution agreement and computer execution time and costs

Characterization of local deformation and fracture behavior in ferrite plus martensite dual-phase steels having different grain sizes

42nd Risø International Symposium on Materials Science: Microstructural variability: Processing, analysis, mechanisms and properties 5–9 September 2022, Department of Civil and Mechanical Engineering, Technical University of Denmark, DenmarkLow carbon dual-phase (DP) steels composed of soft ferrite and hard martensite have been widely used in the automotive industry due to their good strength-ductility balance and large strain hardening ability. DP steels have a wide variation in mechanical properties depending on several microstructural features such as grain size, phase fraction and distribution. Among them, the grain refinement of DP steels is known to be an effective option for enhancing mechanical performance in strength and ductility (especially post-uniform elongation). However, the exact reason for the significant improvement of post-uniform elongation by grain refinement has not been fully understood. It is considered that the characterization of local deformation behavior and micro-void formation/growth behavior in connection with microstructures is an essential approach for understanding the enhanced post-uniform elongation realized in the fine-grained DP specimen. In the present study, we prepared two kinds of DP specimens with mean ferrite grain sizes of 14.9 μm (coarse-grained DP) and 7.1 μm (fine-grained DP), and carefully investigated local strain distribution of tensile specimen and micro-void formation/growth behavior using digital image correlation (DIC) analysis and SEM observations. The fine-grained DP specimen exhibited a gradual strain localization after necking and had sufficient strain capacity that could endure against fracture. The fine-grained DP structure had a great number of micro-voids in the necked region, but almost all the micro-voids maintained a very small size, which was contrasted with the case of coarse-grained DP specimen containing very large-sized micro-voids. Such a significant difference in micro-void size/number characters between two kinds of DP specimens would be one possible reason for exhibiting greatly different post-uniform elongation behavior

ナノ析出強化（フェライト＋マルテンサイト）二相鋼の変形機構

要約のみTohoku University古原忠課

Experimental methodology on the serviceability behaviour of reinforced ultra-high performance fibre reinforced concrete tensile elements

[EN] Design codes include serviceability limit state (SLS) provisions for stress, crack, and deflection control in concrete structures, which may limit the structural design. When drawing on reinforced ultra-high performance fibre-reinforced concrete (R-UHPFRC), the process of cracking differs significantly from traditional concretes. Thus, it remains unclear whether the traditional provisions are applicable to R-UHPFRC or should be reviewed. Uniaxial tensile tie test is an excellent option to analyse and review these criteria. This work proposes a novel test methodology to study the behaviour of R-UHPFRC under serviceability conditions, which lets the study of the global and local deformation behaviour by using different measurement equipment. Two different types of R-UHPFRC ties with variant fibre content were tested. The global average tensile stressstrain curve, cracking behaviour, number, and width of cracks were obtained. Promising preliminary results admitted that this methodology can be useful to propose design criteria of R-UHPFRC under SLS.State Research Agency of Spain, Grant/Award Number: BIA2016-78460-C3-1-RKhorami, M.; Navarro-Gregori, J.; Serna Ros, P. (2020). Experimental methodology on the serviceability behaviour of reinforced ultra-high performance fibre reinforced concrete tensile elements. STRAIN. 56(5):1-13. https://doi.org/10.1111/str.12361S11356

Deformation Induced Lattice Misorientation in Lath Martensite

Effect of plastic deformation on the lattice misorientation in lath martensite was investigated by Electron Backscatter Diffraction (EBSD). As-quenched rod-like specimens were plastically deformed until 9000 N, 14000 N, 19000 N and 21000 N of tensile loading. Grain average misorientation maps were collected by EBSD. It was shown that the average misorientation during plastic deformation increased from 0.887 to 1.156 degrees. Results showed that the density of geometrically necessary dislocations, which caused the lattice misorientation, slightly increased during plastic deformation of lath martensite

Monotonic and fatigue properties of steel material manufactured by wire arc additive manufacturing

In this study, the monotonic and cyclic material properties of steel material of medium static strength produced additively in the wire arc additive manufacturing (WAAM) process were investigated. This investigated material is expected to be particularly applicable to the field of mechanical engineering, for which practical applications of the WAAM process are still pending and for which hardly any characteristic values can be found in the literature so far. The focus of the investigation was, on the one hand, to determine how the material characteristics are influenced by the load direction in relation to the layered structure and, on the other hand, how they are affected by different interlayer temperatures. For this purpose, monotonic tensile tests were carried out at room temperature as well as at elevated temperatures, and the cyclic material properties were determined. In addition, the hardness of the material and the residual stresses induced during production were measured and compared. In addition to the provision of characteristic properties for the investigated material, it was aimed to determine the extent to which the interlayer temperature influences the strength characteristics, since this can have a considerable influence on the production times and, thus, the economic efficiency of the process

Identification of material properties for finite element simulation of the deep rolling process applied to welded joints

During butt welding of structural steels, an inhomogeneous material state across the weld occurs that has a detrimental influence on fatigue strength. In the presented study, the identification of Lemaitre Chaboche elastoviscoplastic model parameters is shown. The identification was conducted for base material, heat affected zone and filler material of submerged arc butt welded 1.8813 (S355MLO) structural steel. The derived constitutive model was integrated into a finite element simulation of the deep rolling process, which has not been investigated before for the post treatment of welded joints. Mechanical process loads were derived, giving first explanations of the deformation behavior